Re: Ruby Gotchas presentation slides

Please keep this discussion going! I'm getting tons of value out of lurking
this thread.
On Apr 1, 2013 4:50 PM, "Dave Aronson" <[e-mail]>
wrote:

> On Sun, Mar 31, 2013 at 2:36 AM, Josh Cheek <[e-mail]> wrote:
>
> > The double vs single quotes doesn't seem like a gotcha to me.
>
> I was debating that one.  The rule is the same in most languages that
> HAVE string interpolation, so yeah, it shouldn't be terribly
> surprising.  But in most languages I've used, one or the other (single
> vs. double) is just plain invalid (for a multi-char string), or
> they're both equally valid, so there being a difference at all is a
> bit of a gotcha.
>
> > The freezing one is good, but should be separated from the constants, as
> > it's really just about variables. You can update the variable, but not
> > modify the object, so you have to know which you're doing. Might also
> > mention that it is for just that one object, so freezing an array doesn't
> > freeze the elements in the array.
>
> Ah, yes, I had originally intended to do something about modding the
> references vs. the object it points to.  Forgot to split that out.
> Array slots are of course simply a special case of that.  I'll split
> 'em out and work on it before the next time I present it.
>
> > Balanced whitespace is good (better example would be `one -1`)
>
> Oooh, good one!
>
> > The parent initialize one doesn't seem legitimate to me, that's how
> > inheritance works, why would you expect anything else?.
>
> IIRC, in some languages, they do automagically run parental initters
> for you by default.  It's been so long since I've done much OO other
> than Ruby, especially with inheritance, that I forget which does what.
>
> > The example for local var in the block seems too contrived. It's only
> ever
> > hit me when I tried to do something like `.each{ |i| sum ||= 0; sum += i
> }`
> > in the loop, in which case it always gets set to zero.
>
> Well, yeah, they're all rather contrived!  I didn't put a high
> priority on thinking up a realistic example, so I'll just swipe yours.
>  :-)
>
> > The idea credit seems out of place, the hash block setting the value has
> > been a common pattern for a long time.
>
> I figured, better to give credit too much and take up extra space,
> than to slight someone by stealing something.  But to make you happy,
> I won't credit your loop/closure var-value-losing example.  :-)
>
> > Frankly, I dislike it because it (a)
> > sets keys on access, regardless of whether or not they will be used (e.g.
> > you could be carrying around thousands of empty arrays),
>
> Good point, I'll add a caveat.
>
> > and (b) changes
> > behaviour of hash such that you must use #.has_key? to see if the key is
> > set, because otherwise, the key is always set.
>
> True, but if you're using it for a specific purpose, there's probably
> a more domain-relevant test.  In the case I showed, someone wanting to
> know if someone knows any computer languages might ask if
> langs[employee].any?.
>
> > I think the
> > Array version of this is a better example,
>
> Also useful... but I think it's still worth pointing out this gotcha
> with hashes too.  I'll make them separate slides, with Arrays first
> since creating them all up front is clearer.
>
> > I'd maybe add lambda vs proc:
>
> Yeah, I thought about delving into that, but it was a bit more
> advanced than I wanted to inflict at that point.  I was trying to keep
> the whole talk under an hour, including Q&A, and the audience has a
> wide range of skill levels.  Maybe I'll just save it for last, and
> skip it if we're running short of time, or their eyes are glazing
> over....
>
> > Might also add method_missing, which is evil (I don't think eval is evil,
> > but using method_missing on code that anyone else uses is sadistic)
>
> Eh... if used judiciously, and correctly (including a super-call if
> not figured out), it can be OK.  And if someone is messing about with
> method_missing, I think they're probably experienced enough not to
> need this presentation.  :-)  But now that you mention it, the need to
> ALSO adjust responds_to_missing, is quite a gotcha.
>
> > Might also add floating point number imprecision.
>
> That's in pretty much *any* language, so I don't really count that as
> a *Ruby* gotcha per se.
>
> > Might also mention when a block gets instance evaled, but you're calling
> > methods on your local context (e.g. a dsl you call from rspec can't call
> a
> > let).
>
> Now you're just making my head hurt!  ;-)  I think I read something on
> that a few weeks ago, that I might be able to TL;DR-ify... or maybe it
> was in the context of JavaScript, where issues of defining "this" are
> critical AND common....
>
> > Might also add nonprinting characters,
>
> Not Ruby-specific enough.
>
> > I'd also put the most relevant ones earlier, when people will be paying
> the
> > most attention.
>
> Ordering is a bit of a tough question.  I was initially trying to put
> the easiest stuff first, so the Ruby-newbies could get some value out
> of it before their eyes glazed over.  :-)
>
> Thanks,
> Dave
>
> --
> Dave Aronson, the T. Rex of Codosaurus LLC,
> secret-cleared freelance software developer
> taking contracts in or near NoVa or remote.
> See information at http://www.Codosaur.us/.
>
>